Method for producing electrodes as well as electrodes produced by the method

ABSTRACT

An electrode for an electrolytic capacitor and a method for producing the electrodes including a conducting electrode material, in particular a foil, such as an aluminum foil. The conducting electrode material, for the purpose of increasing the surface, is exposed to a chemical or an electrochemical etching process. During the etching process, in an etching cell, at least one zone of the surface of the electrode material is covered with an etch-resistant coating and/or a separate protective shielding. After the etching process, the electrode is cut out, punched out or the like worked out of the electrode material such that the etched zone forms at least one margin region, in particular, a margin strip of the electrode.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to a method for producing electrodes for electrolytic capacitors comprising a conducting electrode material, in particular a foil such as an aluminum foil, which, for the purpose of increasing the surface area, is exposed to a chemical or electrochemical etching process. The invention also relates to electrodes produced with such method.

[0003] 2. Description of the Related Art

[0004] In the field of electrolytic capacitors it is known to use, for example, aluminum foils as electrode material, which has been subjected to an etching process, in order to increase the effective surface thereof. In an electrochemical etching process, the aluminum foil is disposed for example between two conducting plates of an etching cell, and the plates are immersed in a conducting solution of electrolytes. The etching process can subsequently take place in different polarization configurations: for example, the aluminum foil is connected to the positive pole of a current source and the conducting plates of the etching cell are connected to the negative pole of the current source, and a continuous or pulsed current flows. A further feasible configuration comprises disposing the aluminum foil between two conducting plates, between which an AC current flows. It is, in addition, known, in the case of anodic foils to carry out an anodic oxidation, after the etching process, which makes possible the growth of aluminum oxide on the foil surface. But, for specific electrolytic capacitors frequently also electrodes with an etched surface are required in which, for example, in the margin region, connecting contacts must be applied. The electrode is to have good electric and thermal contact at these margin regions such that the equivalent series resistance (ESR) and the power consumption are improved when the electrodes are rolled up, for example, for the production of the electrolytic capacitor. Etching impairs such good contacts.

SUMMARY OF THE INVENTION

[0005] It is the object of the invention to provide in a simple manner electrodes which offer, in particular in their margin region, good electric and thermal contact.

[0006] This object is essentially solved in a method of the above described type thereby that during the etching process at least one zone of the surface of the electrode material is covered in the etching cell with an etch-resistant coating and/or by a separate protective shielding. After the etching process, the electrode is cut out, punched out or the like worked out of the electrode material such that the non-etched zone forms at least a margin region, in particular a margin strip, of the electrode.

[0007] With this method, non-etched zones can be simply formed in any shape on the surface of the electrode material such that the subsequent formation of the electrodes their margins are non-etched. Thus, the production method can be adapted to special requirements for specific electrodes. It is in particular possible to use sheet electrode material in the form of webs from which individual electrodes are subsequently punched out for example in the form of strip electrodes which can be wound up. In this way, the production process can be standardized and made efficient for different electrode types, and thereby considerable cost reductions can be attained. In addition, the handling of large, for example web-form, foil material during the etching is simpler than the handling of individual narrow electrodes. Providing contact zones which offer very good electric and thermal contact, can be omitted due to special surface working. The method according to the present invention is suitable for the production of electrodes used as anodes and cathodes.

[0008] In a simple implementation of the method according to the present invention for the production of these electrodes a coating or foil can serve as a shielding deposition, which is applied onto the surface for example by application, emplacement, adhesion or the like and which, after the etching, is detached again. Such a method can be employed especially favorably in particular in the production of standardized electrode types.

[0009] It is also conceivable that a lacquer or a synthetic resin serves as the coating, wherein the lacquer or the synthetic resin is applied by spraying or by means of being brushed onto the surface, and after the etching process, is dissolved by means of an organic solution, for example. With such a method a deposition, which has a complicated geometric shape, can also be readily applied onto the surface. In particular, when using a mask, the zones on the electrode material can be developed precisely.

[0010] In an electrochemical etching the deposition is developed preferably as an insulating material and during the etching process the deposition forms an electric shielding on the conducting electrode material. The insulating material can comprise, for example an electrically nonconducting synthetic material and is disposed between the electrode material and the conducting plates of an etching cell. In this case, the etching electrolyte is not in contact with the shielded zone since the insulating material is in direct contact on the surface of the electrode material such that no etching takes place in the shielded zones.

[0011] According to another implementation of the method, the protective shielding comprises a nonconducting material as a separate element and is disposed in the etching cell between the electrode material and the conducting plates of the etching cell such that these are in direct contact with the electrode material and during the electrochemical etching process form an electric shielding.

[0012] The position of the protective shieldings in the etching cell can be handled especially simply and allows for the desired non-etched surface of the electrode material to be readily reached during the continuous operation of the etching process. To this end, the protective shielding is already disposed in the desired geometry in the etching cell and does not need to be developed as a deposition in each instance on the electrode materials.

[0013] However, a combination of both implementations of the method is also conceivable in which the protective shieldings, can, for example, also serve for fixing the electrode material in the etching cell.

[0014] In the production of strip electrodes, the zones are preferably formed as parallel strips or the like, one spaced apart from the other, as regions extending in the longitudinal direction of the electrode material developed for example as band material.

[0015] If the electrode is to be used as an anode, the electrode material is exposed to anodic oxidation after the etching. The deposition can therein be previously detached from the areas not to be etched, such that the etched as well as the non-etched zones are oxidized. For use of the electrode as a cathode, such treatment is not necessary.

[0016] The etching is preferably carried out with the formation of non-etched zones and, if appropriate, the oxidation is carried out on both sides of the electrode material. The non-etched zones can be developed on both sides of the electrode material corresponding to one another such that the electrodes formed therefrom have the same structure on both sides. In the case of special capacitor types, however, an asymmetric implementation of non-etched zones on the two sides of the material is also conceivable.

[0017] For the production of electrode strips from the, for example, web-like electrode material, corresponding electrode strips are cut out, and preferably at least one longitudinal margin of the strip material is not etched.

[0018] Efficient processing of the electrode material is in particular possible if several, for example, strip-like electrodes are cut out of the sheet electrode materials.

[0019] The present invention further relates to electrodes comprised of a conducting electrode material, in particular a foil formed as a band material, such as an aluminum foil, with a surface which is etched on one or both sides and, if appropriate, anodically oxidized, wherein in at least one margin region, preferably margin strips of the surface, at least one non-etched zone is developed. Zones can therein be disposed on each side of the electrode material corresponding to one another.

[0020] In the development of strip electrodes, corresponding strips are cut out of the, for example, web-form electrode material in the width of the capacitor to be produced therefrom such that preferably at least one margin of the strip electrode is not etched.

[0021] Further characteristics, advantages and application feasibilities of the present invention are evident based on the following description of exemplary embodiments and the accompanying drawing figures. All described and/or graphically shown characteristics by themselves or in any combination form therein the subject matter of the present invention, independently of their compilation in the claims or their reference back.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a schematic illustration of a configuration for etching an electrode according to a first known method;

[0023]FIG. 2 is a schematic illustration of a configuration for etching the electrode according to a second known method;

[0024]FIG. 3 is a schematic illustration of a configuration for carrying out the method according to the present invention with a deposition applied onto an electrode material; and

[0025]FIG. 4 is a schematic illustration of an alternative configuration for carrying out the method according to the present invention with a protective shielding disposed separately in an etching cell between the electrode material and conducting plates.

DETAILED DESCRIPTION OF THE INVENTION

[0026]FIGS. 1 and 2 show schematically the disposition of a conducting electrode material 1 between two conducting plates 2, 3 during the etching process, in which the overall configuration is immersed in a (not shown) solution of electrolytes of an etching cell. In the variant depicted in FIG. 1 of the electrochemical etching, the electrode material 1, for example an aluminum foil, is connected to the positive pole of a voltage source. The two conducting plates 2, 3, in contrast, are connected to the negative pole 5 of the voltage source. The etching subsequently takes place by switching on a DC current or a pulsed current.

[0027]FIG. 2 shows a similar configuration of electrode material 1 and conducting plates 2, 3 which are immersed in a (not shown) solution of electrolytes for the etching process. In this case, the plates 2, 3 are connected to an AC voltage source 6. The electrode material 1 is not connected to a voltage source.

[0028] Purely chemical etching methods are likewise conceivable in which the electrode material for the chemical etching is simply immersed in corresponding etching solutions. In this case, the conducting plates 2, 3 can be omitted.

[0029] In order to avoid etching the entire surface of the electrode material 1, but rather to develop non-etched surface zones on the electrode material 1, according to the present invention, as shown in FIG. 3, in specific, here strip-form zones, an electrically insulating deposition 7 is applied on the electrode material 1, for example a non-etched aluminum foil. The deposition 7 prevents electrochemical corrosion during the subsequent etching process in which the deposition 7 applied on the surface is disposed between the electrode material 1 and the conducting plates 2, 3 in an etching cell. During the electrochemical etching process, current flows from the electrode material 1 to the plates 2, 3 except in the zones shielded with the deposition 7. Shielding acid-resistant depositions, which prevent chemical corrosion, can also be used.

[0030] To apply the deposition 7, first the regions of the electrode material 1 to be etched are covered with masks 8 and subsequently a preferably liquid deposition material, such as for example electrically insulating lacquers or acid-resistant synthetic resins, is applied on the regions of the electrode material 1 not covered by the masks 8. This can take place, such as shown by example, by application with a brush 9, by spraying or the like. After applying the deposition 7, the masks 8 are removed before the electrode material 1 is subjected to the etching process. However, the deposition 7 can also be comprised, for example of an electrically insulating foil which is held on the surface of the electrode material 1 for example due to inherent adhesion or by being adhered thereon.

[0031] After the etching process, the lacquers or synthetic resins serving as deposition 7, which protect the electrode material 1 during the etching against electrochemical corrosion, are removed in an organic solution. In order to obtain strip-form zones, the deposition 7 is comprised of narrow strips, which are applied in the longitudinal direction of the band-form electrode material 1 on its surface at a predetermined spacing one from the other. The spacing of the deposition strips corresponds to the width of the electrode strip required for the production of a wound capacitor. However, other geometric forms of the deposition 7 are also conceivable. This can also be disposed at any other desired site on the electrode material 1.

[0032]FIG. 4 shows a further option for the production of non-etched surface zones on the electrode material 1 according to the present invention.

[0033] Herein separate strip-form protective shieldings 10 of a nonconducting material are disposed in the etching cell in front of the conducting plate 2 and/or, if appropriate, the conducting plate 3. During the etching process the electrode material 1 is placed against the protective shieldings 10, such that the electrode material 1 and the protective shieldings 10 are in direct contact. The protective shieldings 10 thus form an electric shielding for the zones to be covered and prevent here the flow of current. Therefore, etching only takes place in the regions without protective shieldings 10.

[0034] The protective shieldings 10 can be fixedly positioned in the etching cell or can be formed integrally with it.

[0035] The alternative methods represented in FIGS. 3 and 4 for developing non-etched zones on the electrode material 1, as a rule, are applied equally on both sides of the electrode material 1 such that on each surface non-etched zones corresponding to one another are generated.

[0036] After the etching process, the electrode material 1 can be subjected to anodic oxidation in which the etched as well as also the non-etched zones are oxidized in order to develop an oxide layer on the surface of the electrode material 1. In the event that an aluminum foil is used as the electrode material 1, an aluminum oxide layer forms.

[0037] The treated electrode material 1 is subsequently brought into the desired electrode form. In the depicted embodiments with strip-like depositions 7, for example, protective shieldings 10, strip electrodes are cut from the electrode material 1 in the longitudinal and transverse direction such that at least one of their margins is not etched. From sheet electrode material 1 several strip-form electrodes can be cut. The non-etched zones provide especially good electric and thermal contact in particular along the margins of the electrode strips. In this way, the equivalent series resistance (ESR) and the power consumption of the electrodes is improved, if the electrodes developed as foils are, for example, rolled up to form electrolytic capacitors. In the case of electrodes of a band material, efficient fabrication is thus possible.

LIST OF REFERENCE SYMBOLS

[0038]1 Electrode material

[0039]2, 3 Conducting plates

[0040]4 Positive pole

[0041]5 Negative pole

[0042]6 AC current source

[0043]7 Deposition

[0044]8 Mask

[0045]9 Brush

[0046]10 Protective shielding 

I claim:
 1. A method of producing electrodes for electrolytic capacitors including a conducting electrode material, the method comprising: covering at least one zone of a surface of the conducting electrode material with an etch-resistant deposition and/or a separate protective shielding in an etching cell; exposing the conducting electrode material to a chemical or an electrochemical etching process in order to increase the surface thereof; and removing an electrode, after the etching process, from the conducting electrode material such that a non-etched zone forms at least a margin region of the electrode.
 2. The method as claimed in claim 1, wherein the removing operation is performed by cutting or punching the electrode from the electrode material, and wherein margin region is a margin strip.
 3. The method as claimed in claim 1, wherein the conducting electrode material comprises a foil formed of aluminum.
 4. The method as claimed in claim 1, wherein the etch-resistant deposition is a lacquer or a synthetic resin, the lacquer or the synthetic resin is applied by spraying or by being brushed onto the surface of the electrode material, and after the etching process, the lacquer or the synthetic resin is dissolved by means of an organic solution.
 5. The method as claimed in claim 1, further comprising removing the etch-resistant deposition after the etching process, wherein the etch-resistant deposition is applied onto the surface of the electrode material by application, emplacement, or adhesion.
 6. The method as claimed in claim 5, wherein the etch-resistant deposition is a lacquer or a synthetic resin, the lacquer or the synthetic resin is applied by spraying or by being brushed onto the surface of the electrode material, and after the etching process, the lacquer or the synthetic resin is dissolved by means of an organic solution.
 7. The method as claimed in claim 1, wherein the etch-resistant deposition is applied onto the surface of the electrode material using a mask.
 8. The method as claimed in claim 5, wherein the lacquer or the synthetic resin is applied onto the surface of the electrode material using a mask.
 9. The method as claimed in claim 1, wherein the etching process is an electrochemical etching process, and the deposition is developed as an insulating material and, during the electrochemical etching process, the insulating material forms an electric shielding on the conducting electrode material.
 10. The method as claimed in claim 1, wherein the protective shielding comprises a non-conducting material and is disposed in the etching cell between the conducting electrode material and conducting plates of the etching cell such that the protective shielding is in direct contact with the electrode material and, during the electrochemical etching process, forms an electric shielding for a corresponding zone of the electrode material.
 11. The method as claimed in claim 1, wherein the zones are formed as parallel strips extending, spaced apart from one another, in the longitudinal direction of the electrode material.
 12. The method as claimed in claim 1, further comprising exposing the electrode material to an anodic oxidation after the etching process.
 13. The method as claimed in claim 12, wherein the etched and the non-etched zones of the electrode material are anodically oxidized.
 14. The method as claimed in claim 12, wherein the etching process is carried out with the formation of at least one non-etched zone and, if appropriate, the oxidation operation is carried out on both sides of the electrode material.
 15. The method as claimed in claim 14, wherein one non-etched zone each is developed on both sides of the electrode material corresponding to one another.
 16. The method as claimed in claim 1, wherein the electrode material comprises a sheet of electrode material from which a plurality of strip-like electrodes are removed from the sheet of electrode material, and the number of strip-like electrodes correspond to the number of non-etched zones.
 17. An electrode comprising a conducting electrode material having a first and second sides, wherein at least one of the sides includes an etched surface and at least one margin region that forms a non-etched zone.
 18. The electrode as claimed in claim 17, wherein both sides of the electrode material includes an etched surface and an anodically oxidized surface.
 19. The electrode as claimed in claim 17, wherein the margin region comprises a margin strip.
 20. The electrode as claimed in claim 17, wherein the conducting electrode material comprises a foil, such as an aluminum foil, which is developed as band material.
 21. The electrode as claimed in claim 17, wherein non-etched zones are formed on both sides of the electrode material.
 22. The electrode as claimed in claim 21, wherein each of the non-etched zones formed on one side of the electrode material has a corresponding non-etched zone formed on the opposite side of the electrode material.
 23. The electrode as claimed in claim 17, wherein at least one margin of the electrode material is not etched.
 24. The electrode as claimed in claim 17, wherein the electrode is produced by: covering at least one zone of a surface of the conducting electrode material with an etch-resistant deposition and/or a separate protective shielding in an etching cell; exposing the conducting electrode material to a chemical or an electrochemical etching process in order to increase the surface thereof; and removing the electrode, after the etching process, from the conducting electrode material such that a non-etched zone forms at least a margin region of the electrode. 